This invention relates to a three-roller type constant velocity universal joint, and more specifically to such a joint in which three drive rollers are carried by yoke pins on one of two drive members and are engaged with respective guide grooves formed in the other drive member to provide constant velocity universal drive and permit the two drive members to be angularly tilted with respect to each other.
Constant velocity universal joints to the three roller type are described in the literature, for example, in U.S. Pat. No. 3,125,870. Typically, a joint of the type comprises one drive member with three yoke pins and three rollers rotatable about the axes of, and movable axially of, the respective yoke pins, and the other drive member with three guide grooves engaged with the three rollers.
The universal joint of the construction described operates in the following way. As one drive member is tilted with respect to the other while power is being transmitted through the joint, the yoke pins of one drive member are tilted, too, within the other drive member. Accordingly, the rollers on the respective yoke pins rotate around the pins and, guided by the guide grooves in the other drive member, move rectilinearly in parallel with the rotational axis of the other drive member while, at the same time, inclining and sliding in the guide grooves under the urgings of the yoke pins tilted by the angular shifting of the two drive members relative to each other.
In the foregoing operation, the repetition of relative angular shifting of the two drive members causes the rollers to continue simultaneously a combined motion, or a combination of their rolling motion in engagement with the guide grooves and their skew sliding motion in engagement with the grooves that results from their linear travel in the grooves and from the tilt of the yoke pins. This combined motion is so rigorous for the guide grooves as well as for the rollers that it hastens their surface fatigue. In addition, the skew sliding motion relative to the guide grooves causes the rollers to deviate in their contact with the yoke pins. These unfavorable conditions bring a number of disadvantages, including reduced strength and shortened life of the rollers and yoke pins.
Another prior art universal joint of the type is disclosed in U.S. Pat. No. 3,818,721. The joint carries rollers rotatably on trunnions, or yoke pins, by means of self-aligning bearings so that the rollers are restrained from their movement axially of the yoke pins while their rotation around, and tilting relative to, the yoke pins are permitted. In the patented joint the rollers cannot move axially of the yoke pins, and therefore they move within drive channels or tracks, or guide grooves, with arcuate loci. Consequently, the peripheral speed on the outer periphery of each roller is greater than that on the inner periphery, and the roller performs both rolling and sliding motions with respect to the associated guide groove. As a result, the rollers and guide grooves tend to suffer from premature surface fatigue under conditions as severe as with the joint of the abovementioned U.S. Pat. No. 3,125,870.